Some airports have manned counters for left luggage (London for example) where you can leave things over several days. Some are only 24 hours. I have never had anything taken from them, but you need to call ahead to see how long you can store things and how large things can be. If the SCUBA includes a tank, there may be some problems with that, at least I would hope they just wouldn't let you store a tank of compressed gas at an airport anymore (I know it's only air, but they don't know that)